Money is the currency for which you upgrade businesses and get unlockables.

Money is generated by either tapping actively or passively from businesses.

Other sources of money include rocket present, Make it Rain, gem upgrade, or from offline progress.

Amount of money In-game notation Engineering notation
0 0 0
1000 1K 1E3
1000000 1M 1E6
1000000000 1B 1E9
1000000000000 1T 1E12
1000000000000000 1aa 1E15
1000000000000000000 1ab 1E18
1000000000000000000000 1ac 1E21
1000000000000000000000000 1ad 1E24

The numbers go until the limit of used computer number format. Realistically, they go until infinity as it is imposible to reach the end of numbering format