The word "accompany" means to go somewhere together with. For example, one of the most common uses of this word is in this sentence:

All children must be accompanied by an adult.

You can see this on signs at places that are dangerous for kids, like swimming pools.

It can also be used to talk about documents that need to be sent together:

Please note that all applications must be accompanied by two letters of recommendation.

The word "accompany" is quite formal, so it's mostly used in writing.