open
You must open a file before you can read its contents.
close
When you are done with a file, you should close it.
read
Will read the entire contents of a file as a string. This is often used in an assignment statement so that a variable can reference the contents of the file.
readline
Will read a single line from the file, up to and including the first instance of the newline character.
readlines
Will read the entire contents of a file into a list where each line of the file is a string and is an element in the list.
write
Will add characters to the end of a file that has been opened for writing.