So, say I am using Snapchat, can my internet provider see that I am using it?
Today practically all of the information sent on the Internet is encrypted. There are only a few exceptions.
This encryption is typically unbreakable by an ISP (you see warnings in browser windows, or your applications don't work et al). They might be breakable by some governmental agents. There are only a few exceptions.
However, even an encrypted communication gives some information to a possible eavesdropper:
- Only encryption still does not hide, with whom are you communicating. Snapchat communicates with some central servers in the USA.
- Only encryption still does not hide, when and how many data packets did you sent.
These might be enough to collect a surprisingly many information from your communication.
If you use VPN correctly, they can't see that you are snapchatting, but they can probably see from (2) that you are chatting. They can also see that you use a VPN.
If you use snapchat without a VPN, they can see that you are snapchatting, but they can't see what.
Note, governmental security services have significantly more power than an induvidual ISP. For example, without a VPN, they can estimate with high probability, with whom are you snapchatting. Induvidual ISP can do this only if your partner is the customer of the same company (and it is mostly an irrelevant info for them - they want your money, not your chat messages).
Of course any governmental agent (or any agent with the same power) having power over the snapchat, can ask them to simply give them their logs. Thus, you have more reason to fear them. Snowden's surprising results is that they are doing it automatically, with practically all internet users of the world.