Over 3 million people took these 5 online courses in 2019—here's what they teach you

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As technology continues to transform business, workers are using technology to transform themselves throughout their careers.

Today, one of the most common ways for workers to do this is by taking a course online.

There are several online education providers offering free and low-cost courses for workers hoping to "upskill," meaning they want to pick up a new skill that can help them advance their careers.

One of those providers is LinkedIn Learning, which costs about $299.88 per year but is often offered to students by their universities or to workers through their employers.

Approximately 93 million workers watched LinkedIn Learning courses in 2019.

LinkedIn recently analyzed their user data to determine their most popular courses of the year. More than 3 million people took these five courses:

5. Python Essential Training

Course description:

"This course covers the basics of the language syntax and usage, as well as advanced features such as objects, generators, and exceptions. Learn how types and values are related to objects; how to use control statements, loops, and functions; and how to work with generators and decorators. Bill also introduces the Python module system and shows examples of Python scripting at work in a real-world application."

4. Project Management Foundations

Course description:

"Project management is a start-to-finish approach to getting things done and making projects more successful. It's a profession, but it's also a set of techniques that anyone can apply to achieve goals and manage project work more effectively. Project management can be used to guide small, simple projects as well as complex enterprise-wide initiatives."

3. Online Marketing Foundations

Course description:

"Learn how to promote your business effectively online and develop a targeted online marketing strategy that engages potential customers throughout the digital landscape. In this course, Brad Batesole explains today's digital marketing techniques in simple terms, demonstrating how to build a successful online marketing campaign for all digital channels: search, video, social, email, and display."

2. Cert Prep: Project Management Professional (PMP)

Course description:

"This certification training course teaches critical project management concepts from the exam and offers study guides and sample practice exams to hone your test-taking skills. This course also fulfills the 35-hour education requirement needed to sit for the exam and provides 35 PDUs for current PMPs who need the credit to maintain their certification."

1. Excel Essential Training

Course description:

"Learn how to enter data, organize data, perform calculations with simple functions, work with multiple worksheets, format the appearance of data and cells, build charts, and create PivotTables. Find out how to use the IF, VLOOKUP, and COUNTIF family of functions. See how to use data analysis tools, including Goal Seek and Solver. Discover how to automate tasks with macros, manage data, and more."

According to LinkedIn, the most popular course of 2019 was "Excel Essential Training."

Emily Poague, vice president of LinkedIn Learning, tells CNBC Make It that her team wasn't surprised to see the Excel course come out on top because it is a general office skill that can apply to a wide range of workers in a wide range of industries.

Similarly, getting a certification in project management can be useful to a wide range of professionals.

A course that teaches the fundamentals of Python was LinkedIn's fifth most popular course in 2019. Python was also one of the most in-demand tech skills of 2019, according to Indeed.

Andrew Flowers, an economist at the Indeed Hiring Lab, says that Python is the ideal skill to learn in the new year because it is in high demand (about 18% of tech job postings asked candidates to understand Python in 2019) and also because it is designed to be easy to read and learn.

"That is the driving force, ultimately, behind Python's success," he explains to CNBC Make It. "It's very readable. It's not a sharp learning curve."

Python can also be used for a wide range of purposes, from back-end web development to data analysis and artificial intelligence.

While these specific courses proved to be incredibly popular, the topic that learners took the most courses in overall has nothing to do with technical skills.

"The most popular topic that people spent time learning was communication, and there's a couple of reasons for that," says Poague.

One reason is that there is a large volume of communication classes offered online.

But also, Poague notes, a wide range of workers appear to be deeply invested in collaborating with their colleagues.

"Communication is one of those skills that's universal," she explains. "It's something that everyone feels like they need to work on."

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