Patrick Stewart, well known for his role as Captain Jean-Luc Picard in "Star Trek: The Next Generation", and Peter Capaldi, who plays the character, Doctor Who, in the popular British show, have joined actors Cate Blanchett and Colin Firth in the UNHCR's "#WordsMatter" campaign.
The campaign is aimed at using words with greater care.
In an online video, UNHCR outlines that a "migrant" is someone who "chooses to move" country for reasons such as education or family reunions, while a "refugee" is someone "running for their life," due to conflict or persecution.
Overall, the key difference UNHCR outlines is that migrants are "free to return home," while refugees cannot.
"Words matter – and it matters how the words 'refugee' and 'migrant' are used, because they determine how governments will respond to this crisis," Laura Padoan, external relations associate at UNHCR UK, told CNBC via email.
"Refugees are defined and protected in international law and that means governments have a responsibility to meet those obligations to protect refugees. That is why words matter and why we have enlisted the support of celebrities to help us get across that message."