But did you ever stop to think what this means? What are terms and conditions, and why do you have to agree to them?
Read on to find out more.
Terms and conditions are rules you have to agree to before you can use certain products or services, like social media.
Last year, Newsround found out that many of you have signed up to have social media accounts.
The companies that run these networks - for example, Facebook, Instagram, Snapchat or WhatsApp - all have their own terms and conditions that you have to agree to before you can have an account with them.
For example, they might say that you have to be a certain age to have an account, or that the company is allowed to use any pictures you post however they like.
You might hear of terms and conditions being referred to as Ts and Cs.
You aren't allowed to use these sites without agreeing to the terms and conditions.
So many people - including adults - don't read them because they just want to get on and use the site or app.
They don't think that there's any point wasting time to go through them, which means they don't know what they've agreed to.
Also, the list of rules can be extremely long and complicated - and written in technical language - which can make them difficult to understand.
This means that many people may not know what they've actually agreed to.
It is important to make sure you understand what you are agreeing to so that you know exactly what you've signed up for.
You don't want to get a nasty shock later because you didn't fully understand something that you'd agreed to a while ago.
Jenny Afia, a lawyer who knows all about terms and conditions, says that to make sure you don't get caught out: "Get help from parents or teachers to understand what the terms and conditions mean."
"It's important to be aware of what you're signing up to."
When you sign up to have a social media account, you may have to tick a box saying that you agree to the terms and conditions.