Sales incentives is usually a program to motivate (sales reps) people to surpass what has been set. Called SPIFs (sales performance incentive funds or SPIF ( or called SPIFFs (with an extra F)) but the incentive can be non financial as well (like a dinner meeting with the CEO or a trip to an exotic destination or a day off)) but usually cash is given out as a reward.
SPIFFs can also be team based to promote and not just individual based.  Team SPIFFs are used to promote camaraderie and drill in the fact that it is the team that matters. Team SPIFFs can be a team experience, like dinning,  cooking with a chef, viewing or playing a sport, spa afternoon etc.
Compensation design is what is paid on the whole, including incentives. For most revenue people, it is usually a pay for performance strategy. Compensation design includes items like
Why do sales incentives matter?
When done right, SPIFs (SPIFFs) are a motivator and a recognition tool that the company is rewarding their over and above contribution. However, when not done right SPIFs (SPIFFs) can eat away into the profit margins (and sometimes result in negative profit margins).  Ie. the cost of a SPIFF is more than the margins from generating that revenue from selling that product/service.
Why does compensation design matter?
If not designed right, recruiting becomes an issue as does retention. Said another way, without the right compensation design, it will be hard to hire people and harder to keep people.
Sales reps will not join the company because the compensation design / structure is really complex and difficult to understand or is just not right for them.
There companies and industries that are 100% commission based - like the financial industry. and there are companies that are 100% salary based like in the semi-conductor industry. Semi-conductor companies went to 100% salary based sales roles industry went to 100% salary based
