As or Like?

AS can be:

- a preposition meaning in the capacity of / in the function of like in the sentence:
She works as a teacher.

- but it is usually a conjunction of manner and goes therefore followed by a verb form, for example:
When in Rome do as Romans do.

- It also appears in comparative structures:
Peter is as tall as a my brother.

- In the group such as it means like:
There are different ways of travelling such as (=like) walking, flying or driving.

LIKE

Is a preposition and goes therefore followed by a noun. It expresses similarity:
She feels like a rolling stone (=in the same way as)
It was like a dream (=similar to)

Like is a preposition and is therefore followed by pronouns in the object form.
They said they didn't want people like me in that group.

It can also be followed by a verb, in the -ing form
There's nothing like fishing from a boat.

In fact, when we want to ask about the description of something we use:
WHAT IS something LIKE ? which is quite different from
HOW is something /someone ? where we become interested in personal state, etc.

Source: http://english.baladre.org/sedaviwebfront/asliketheory.htm

Online quiz: As or Like?

Spanish explanation and examples.

More Spanish explanations: I and II.

As or like? Matching exercise.

As or Like Quiz.