Like and as are often confused in English. They can both be used to talk about how things are similar.
Like is followed by a noun or pronoun. For example, “I’mlike my sister”, or “Like my sister, I have brown eyes.”
As is followed by a subject and verb. For example, “She’s a good student, as her brother was before her.”
However, in spoken English, like is often used instead ofas. “She’s a good student, like her brother was before her.”
As is used with a preposition, such as, “As in the 1960’s, the population explosion will cause some problems.”
We can use as in certain expressions, such as “as you know”, “as you requested”, “as we agreed”.
We also use as…..as to give comparisons. For example, “He’s as clever as his sister.”