As you might've been able to tell from the map, the majority of things to do are all tightly packed into a relatively small area on the south-west coast of Bali just above the airport - we call it "The Canggu Area" and it's basically the tourism and expat hub of the island.
What's confusing and important to know about this area is that it's not actually very big, Canggu itself you can drive across in a few minutes (if the traffic's good), so when people are coming to Canggu and looking for accommodation they often don't consider Berawa, Umalas, Pererenan, etc. even though they're basically all the same place, or they'll see a dinner spot in Seminyak and decide against it because they assume it's far, even though it's actually only 5 minutes away - we definitely recommend just having a look on Google Maps at the distances and journey times between locations to put it into perspective, it's a really small area! For that reason, we call everything from Seminyak to Seseh "The Canggu Area!"
Pro Tip: Berawa is the most central part of The Canggu Area, so it's probably the best place to stay if you really want to explore all around - sometimes the traffic can get really bad, so you can save yourself a lot of time by positioning yourself in the middle.
Pro Tip 2: It gets quieter and less populated the further North and up the coast you go, so Seseh it mostly rice fields with a few villas and cafes, whereas Seminyak is not far off a city, just without highrise buildings.
The Canggu Area is great because it's the most developed and has the best access to amenities on the island, and that's actually why we live there! If you're coming for a month or more it's definitely a good base from which you can do trips to other areas, and if you're coming short-term it's still really worth visiting.
But it's also worth noting that it's the busiest and most chaotic part of Bali, and it's not the place with the most natural beauty, so if you're coming to get away from civilisation, either stay more on the North side, or just avoid The Canggu Area entirely and head to one of the areas below.