Like can mean some different things:
1. We can use to like to say that we find a thing is good:
2. We can use like for "the same as" or "nearly the same as":
3. We can also use like for "the same way as":
4. In a question, we can use like to ask people to talk about a thing, or to say if they find it good or not:
5. We can also use like as "for example":
6. In British and American English young people, when talking, have recently started using like as an extra word in the middle of sentences. Sometimes they use it to report what someone said, especially when mimicking the way they said it. This should never be used in writing:
As works in the same way as example 2 - comparing two things using either the word "like" or the word "as" is called making a simile (As big as an elephant). It may be better to use the word "as" for this to stop confusion with example 1.