you recieve a fixed monthly salary called base-pay. this is based on your rank and also years in service. It is split in half and paid out in bi-monthly installments usually on the 1st and 15th (some months differ, and you can get paid 3 times in a month, federally observed holidays alter it etc, but generally 1st and 15th via direct deposit)
there are two components to your 'rank:'
Grade - the actual rank/pay grade you wear on your uniform, and
TIS - Time in service (in months)
(there's another called TIG [time in grade], but it doesn't affect pay. it's just used to determine who the ranking person is)
when you enlist, you are paid as an E-1 (enlisted 1) with <1yr TIS
for like an E1 with <12m TIS:
go to the row with e1, then check the <1yr column
an E4, with 48m TIS [4years]:
you would go down to e4, then over to the 4 year column.
if that E4 happened to get pinned e5, and still had 49m TIS, you would then go down to the e5 row, and again to the 4 year column to figure monthly salary.
say that e5 is coming up on his 5th year in service, when he finally hits 60 months TIS, he'll recieve a 'raise.' for that you would go to the e5 row, then over to the 5 years {60m TIS} column.
that's just basepay though, there are other things like BAH, BAS, BAQ, special/hazardous duty pays (SDAP), lots of other stuff. not to mention generally pay also generally goes up in november to keep up with inflation etc.
another thing, those amounts on the chart are before taxes.