Preposition and Conjunctions

Like

Like can be used as a preposition, it means something is similar to or resembles something else. For example:
- She looks like my friend Mona. (She looks similar to Mona)
- She sings like a bird. (Her voice reminds me of a bird)

As

As can be used as a conjunction to show similarity, it means to do something in the same way as something else. For example:
- Do as your teacher says. (Do the same as what your teacher says.)
- I called John as you asked. (I called John, which is the same as what you asked me to do.)

As can also be used as a preposition, it is used to refer to a particular event or situation. For example:
- I used to work as a teacher.
- He's younger than his friends, but they treat him as an equal.
- He started as a one-man business, but now he employs over 200 people.

Like or As?

Like and as (conjunction) can have similar meanings. Here's where you use each one:

Like is used with any kind of noun, for example:
- She's like an angel.
- My brother is like me.
- Reading a book is like having a conversation with the world's greatest thinkers.

As (conjunction) comes before a subject + verb, for example:
- Don't change anything, I like it as it is.
- Do as you like.
- We left early as you suggested.

Source: 1-language.com