Need with geometric sequence and explanation

Example using this sequence of numbers:

4,6,8,10

4 is the first “term” or “element” of the sequence.

6 is the second term and so on.

The three dots at the end are indicators that the sequence will continue infinitely.

Using this equation:
an = a(1) • r^n-1

an = the nth term (which every term you are finding)
a(1) = 1st term in sequence
r = common ratio