I'll try my best for a quick overview next to the links provided by
@Durge Driven. Please note the top speeds depend on the track, car setup and track conditions and are only ballparks given withour much research. I'm also not extremely knowledgable on the dirt racing series
Also, somebody please correct my errors.
Formula 1
Open wheel cars, currently 6 cylinder turbo hybrid engines, rear wheel drive. Cars are built by the teams adhering to the rules and regulations. Run on tarmac tracks, depending on setup they reach 300-330km/h. Notable races are imo Monaco and Silverstone.
Endurance racing
Several classes of racecars run together, depending on the race it goes from several classes of Prototypes (LMP1, LMP2, LMP3, DP-i) through GT cars (GTE, GT3) down to smaller touring car classes. Run on tarmac tracks, races are anywhere between 3 hours and 24 hours in lenght. Usually 3-4 drivers share a car and switch on pit stops. Engines vary wildly between the cars, but range from hybrids to turbos to NA cars, top speeds range from 330 km/h for the highest prototypes to ~240km/h for the lower touring cars. Notacbe races are Le Mans, Spa and Nürburgring.
Nascar
Somewhat brutish "touring" cars. Heavy and unwieldly, big V8 engine block in the front. They can reach way above 300 km/h in the right conditions. They come in three classes with the Cup Series being the top class. Usually do oval races but are also seen on tarmac tracks. Notable race is the Daytona 500.
Indy cars
Indy cars are open wheel cars that use a spec chassis and either Honda or Chevrolet engines, which means the cars are all the same in comparison to F1. They run on tarmac road circuits with bigger wings reaching ~320 km/h, or on ovals with smaller wings where they can reach over 400km/h in some cases. The cars use a V6 turbo engine. Notabe race is the Indianapolis 500.
Motor cross
"Moto Cross" is run on dirt tracks on dirt bikes, with several classes of bike depending on weight and engine (2-stroke, 4-stroke, power etc). The tracks are ususally stadium tracks with built in ramps and jumps and tight turns. Top speeds are not really a thing here, but they should be around 80-100 km/h on certain tracks I think.
Rally
Rally's main events are raced on point-to-point tracks on different surfaces, tarmac, dirt, mud, snow, some stages are run at night or in the morning/evening. Rallys are timed events, that means cars don't race each other directly like in circuit races, but have cars start with a few minutes between each other and whoever sts the fastest time wins. Cars are ususally small hatchbacks with 4-wheel drive and range aropund 300-400hp. Top speeds are again not really a thing here, but depending on setup they can reach up to 200+ km/h.
Rally cross
Rally Cross uses similar cars to Rally, but they run on circuits instead of point to point. Usually part of the circuit is tarmac, part is dirt. They run against each other. Races are short, ~5-6 laps going for ~10-15 minutes. Once per race a "joker lap" must be taken which is a short alternative route. That can be used strategically to avoid traffic. Cars usually are a bit lower powered than rally cars are reach much slower top speeds, as they are not really that important.
Moto GP
Circuit bike racing, with the Moto GP being the top class. Top speeds are around 330km/h. Lower classes are the GP2 and GP3.
Truck Racing
Tarmac curcuit racing, but in 5 ton trucks. Usually V6 Turbo Diesel engines with 1300 hp and 3000nm torque, run twin tires at the back. European series are capped at 160km/h. Brasilian series can reach up to 240km/h but usually don't and have a speed trap on the longest straight that must not be crossed faster than 160km/h.
BTCC/WTCR
"British Touring Car Racing" and "World Touring Car Racing", usually small hatchbacks with 300ish hp. Mainly front wheel drive and very similar to each other. Close racing, can reach ~230km/h
Super GT/Ex-DTM
Japanese race cars, a mix between prototypes and touring cars. They are tube frame bodies with carbon body panels that resemble the car they want to represent. 500ish HP, top speeds around 300km/h. DTM raced very similar cars (the so called Class 1 regulations) until 2020 but has since switched to GT3 spec cars because of costs.
Hill Climb
Point-to-Point races. Think of Rally, but only on tarmac and only uphill, hence the name. Wildly varying cars including custom cars, old Formula cars, trucks, toruing cars, and so on. HP and Top speeds can range from low to high to ridiculous. Notable race: Pikes Peak
