The read() will read the whole file at once and then print out the first characters that take up as many bytes as you specify in the parenthesis versus the readline() that will read and print out only the first characters that take up as many bytes as you specify in the parenthesis.
If you have a file (test.txt) :
with open("test.txt", "r") as file:
line = file.readline()
I hope this helps you understand the difference between them.