My 2000 arctic cat 500 auto ATV doesn't start with the start button. I can start it if I jump the starter relay. Does that mean I have to replace the starter relay?

What's the difference between a starter solenoid and a starter relay?
The specs call for relay #3530-001 for about $80 but I found a starter solenoid #SND6058 for $25 that is supposed to do the same job. Are they interchangeable?

Thanks