'Like' means 'similar to'. Crocodiles are like alligators = Crocodiles are similar to alligators So, if you say, for example: 'I worked like a slave' (un esclavo) you mean that you worked very hard. This doesn't mean that you really were a slave! However, if you say: 'I worked as a waiter in a restaurant'. you mean that you really were a waiter. This was your job. We can also use 'as ...as' for comparatives. You aren't as tall as your father. I study as much as I can.