Battery platform: 1 battery for all your tools
How does it work?
You can use the battery of a battery platform on different tools that all share the same battery platform and voltage. This means it doesn't matter whether you use a drill, lawn mower, or circular saw. These all work on the same battery. Each brand has 1 or multiple battery platforms. For example, Bosch DIY has the POWER FOR ALL 18V battery platform, but also the POWER FOR ALL 36V platform.
What are the advantages?
The greatest advantage of a battery from a battery platform is that you only need 1. It's useful to have 1 or 2 extra batteries, of course. If you work on longterm jobs, you can easily replace an empty battery with a full one. If you have batteries of a battery platform, you don't have to buy a complete new set if you want a new tool. A separate 'body' without battery and charger will be sufficient.
Not completely universal
The voltage of a battery needs to match your tools. A 14.4V battery doesn't fit on an 18V drill, even though they're part of the same battery platform. The amperage of a battery is something to check too. The lower the amperage (1.5Ah, for example), the faster the battery runs empty. So if you need to be able to use it for a couple of hours back to back, you should choose an amperage of at least 5.0Ah.