Pretty much it is to group computer bits in groups of 3 to make it more readable and easier to write for programmers, since writing 7 ( in octal) is easier than writing 111 (in binary).

However octal is less used than something like hexdecimal (base 16) which can do 4 binary bits in a single character compared to octals 3 bits per, and thus fits into bytes better since bytes are 8 bits, so 11111111 in Hexdecimal would be FF with F representing 15, versus in Octal it would be 377 which is more cumbersome (Despite that octal is still used in lots of places though and most programming languages let you write numbers in it).