There may be a number of issues with the lawn mower. The motor may need oil or gas. The intake filter may be too dirty, clean it up then put it back in when it is dry.
The blades might not be able to spin around, maybe something is obstructing them, causing the machine to not turn over the engine / motor.
tow it
I have a 14.5 Briggs and Stratton engine on a Ranch King riding mower that will not start. After spraying starter fluid into the head, and air cleaner it fires for a second, but will not run. It is getting gas.....coil??? or something else?
It maters what type it is but is properly the fuel line
Try spraying start gas into the air cleaner.
Turn your blades off.
It depends what engine it is. If it was just a toy car yes... but if it was a mower no. what about a 50cc atv??
Its ether siezed or if its electric start the silenoid might be bad.
If you have a simple push mower, the governor is a small plastic fin attached to your throttle. The fin is underneith the engine cover in the area that spins (part that you pull on a pull start mower)
It depends on if you bought a pull start mower or a power mower. The pull start mower will have a handle you have to pull hard to start it. The power mower should have a button that simply turns it on. Make sure there is gas in the pull start mower.
if your rider mower uses petrol/gasoline then you can remove the spark plug after you have tried to start it and if there is fuel getting to the engine the plug will be wet with fuel,if however it is dry then no fuel is present.
your question needs more detail - make and HP of engine would be a good start.
I am assuming that the mower doesn't start.... My first guess would be that you are not getting spark to ignite the gas in the engine. Check to see if you have spark at the spark plug.