There are multiple different game modes in CSR racing. First and foremost, there are "Regulation Races". These races in particular are unlocked from the very beginning, and have three different difficulties (unlocked by beating "crew" members on Tier 1) that reward higher cash prizes the higher the difficulty.

Secondly, there are "Daily Battle". These are races that unlock at midnight and which you can play again after a certain amount of time. If you lost the battle, you can do it again in 60 minutes and if you won you will have to wait approx. 4 hours for cash races or 5 hours for gold races.

Thirdly, there are "Ladder Races" that are unlocked from the start and consist of 24 races that go up in difficulty (and reward prize) with every one you beat in it.

Next are the "Crew Battles" which are the corresponding Tier "crew" to beat on the city, up to the Crew Leader which unlocks a new Tier once beaten.

"Restriction Races" are unlocked on the Tier 2 Ladder events, it includes races with a specific restriction in upgrades or car stats.

Car Specific events are unlocked at Tier 3. you can only race with a specific car and must purchase upgrades to progress through it.

Manufacturer Specific is unlocked in Tier 4. Similar to Car Specific, it only lets you race in cars from a certain manufacturer. this means different cars can be sed in it. e.g. you may find a Nissan GTR go up against a Nismo 400r. they are different cars but from the same manufacturer

Then, there is the "Race Your Friends" mode (latest added), which lets you compete against the modded cars of your friends to be the best on the leaderboard through Facebook!.

"Multiplayer" is a mode that is unlocked once you beat the Tier 1 Leader.

When you beat Errol, the Tier 5 Crew Leader, you unlock the higher tier events for lower tiers. the only one that is not unlocked is maufacturer specific, and this is unique to Tier 4

World Tour introduces more events. There is crew Battle, where you upgrade a specific car and race the corresponding crew member. you must face their entourage between their races. World tour also introduces more restriction races. one for low tier cars (Either Tier 2 or Tier 3) and restriction races for the crew cars. the low tier races correspond to the crews location:

Crew location Low Tier car
Veloci Italy Alfa Romeo 4C
Armada Europe Mercedes C63 AMG
Spitfire England Jaguar F-Type
Rushmore America Ford Mustang Boss LS