It took me a while to understand offset as well, don't feel ignorant.
The short answer is:
The higher the offset (+) number the center line of the wheel becomes closer and closer to the inside of the fender or closer and closer to your brakes and suspension parts.
The lower the offset (+) and moving down real low into (-) numbers like
@Trey Hardy mentions the further outward the center line of the wheel becomes further away from your brakes and suspension parts and will eventually start to position the wheel outside the fender edge and "poke" out at some point (this varies per vehicle).
For Example:
Your current OEM wheels are 22" x 9" with a +24 offset. Offset is always provided in mm so, the OEM wheels in reference are +24mm offset.
3/8" = .375"
.375" = 9.525mm (roughly due to conversion)
So, if you wanted to buy new 22" x 9" wheels that are roughly 3/8" further AWAY from your brakes and suspension you would be looking for a set of 22" x 9" wheels with a 9.525mm (let's round up to 10mm) lower offset.
The wheels you'd be looking for would be 22" x 9" with a +14mm offset.
Wheel design and the shapes of the spokes can certainly impact brake caliper clearance also.
Here are 2 sites you can use to plug in different wheel and tire dimensions and get a rough idea on how the fitment would change or be impacted:
Tire Tech Information - The Wheel Fitment, Tyre Stretch, Rolling Radius and Speedometer Error Calculator. Play with specs, try different settings, compare results
www.wheel-size.com
Alloy Wheel & tyre fitment calculator - it calculates inset, poke, speedo error, tyre stretch and loads more.
www.willtheyfit.com
Keep in mind the 2 sites above are just tools and the information is not vehicle specific.
Getting some spacers for your OEM wheels isn't a bad idea and probably the cheapest option. I have purchased aluminum spacers and hub centric rings for many vehicles I have owned (including my Yukon) from here:
https://www.motorsport-tech.com/index.html
They can pretty much make any kind of wheel spacer, adaptor, or hub centric ring you want.
A few things to keep in mind on spacers:
1. Make sure they are hub centric to both the hub on your vehicle and the hub center bore of your wheels. If using OEM wheels this is the same dimension. If purchasing aftermarket wheels this could be 2 different dimensions.
2. There are 2 different kinds of spacers; Slip-on and Bolt-on. Spacers that are around 10mm thick would be the slip-on style. This may require some ET Lug Nuts (extended thread) or some extended wheel studs. You would have to bump up to a minimum of .75" (19mm) thick spacer to get the bolt-on style that have new wheel studs built in.
You can browse that Motorsport-tech site for more information on the differences between slip-on and bolt-on.
I previously ran some 22" x 9" +15mm offset wheels with 285/45/22 tires on my '15 Yukon XL Denali and the wheel and tire set-up was right about flush with the fender with a factory alignment.
Hope this helps.
