cp(1) copies files. DOS users will notice its similarity to the copy command. There are many options for cp, so you should have a look at the man page before using it.
A common use is to use cp to copy a file from one location to another. For example:
$ cp hejaz /tmp |
This copies the hejaz file from the current directory to the /tmp directory.
Many users prefer to keep the timestamps preserved, as in this example:
$ cp -a hejaz /tmp |
This ensures that the timestamps are not modified in the copy.
To recursively copy the contents of a directory to another directory, you would issue this command:
$ cp -R adirectory /tmp |
That will copy the adirectory directory to the /tmp directory.
cp has many more options that are discussed in detail in the online manual page.