I am having a home built and 100 Amp service is the standard/ How does this compare
I always had 220 wiring... Can someone explain this and do I need to upgrade to a higher amp for any reason?

Relax,

100 Amp is the current "Minimum" standard. If the electric has not been run yet, I would suggest that you go to 200 Amp, particularly if you have a large home and plan on any expansions like a wood shop or machine shop.

You have to have 240 regardless of the amperage being delivered to your home. 240 VAC is created off the SEP (Service Entry Panel or Main Panel box)

The Power Company will put two Load conductors into the SEP and either a Neutral Grounded wire or both a Neutral and a Ground wire to the SEP.

240 is made by connecting two adjacent breaker positions each supplying 120 VAC. Which gives you a 240 VAC "line in".

By the way, the current standards are 120 VAC and 240 VAC.

In the US, residential service brought to he transformer from the utility is single phase.

The transformer actually creates two sources of 120 Volts AC 180 degress out of phase with a common point called neutral. This provides 240 V service. In your 100 AMP case, you have 100 amps of 240 VAC available OR 200 Amps of 120 available and combinations. Note the OR.

Lot's of things determine the size of a service. Big ones are:
All electric home.
Electric range
Hot tub
Pool
tankless water heaters
Electric dryer
Number of baths
Workshop
Air conditioning (how big)
Electric baseboard heat

Floor plan

200 Amp panels are larger and have more slots.

That's the why.

Do you have to upgrade? Depends on many variables. The big ones shown.

100 Amps service Most always have 240 volts in panel.

ALL newer services have 120/240v. By newer I mean within the last 60+ years.

100A is the code minimum. It is really a meaningless term to say a 100A service will have 200A @ 120v. It IS 100A @ 240v, or the potential for 24,000 watts.

Cranberry, you are confusing volts with amps. Tow completely different things.
I am HIGHLY surprised that they even offer a 100A service. I bet they are barely code legal at 100A. Do they provide a load calculation?

I see ABSOLUTELY NO reason to install a 100A service in a new home. I don't care if it is only 1200 sq/ft.

If you are planning any growth(Garage, welder, Jacuzzi,Insta Heat... )Then Go with 200 Amp Service if you can, It does NOT use more power. The Time, Labor, Permiting(if they will allow the upgrade, in the future)I would get now if I could, even if money was a problem.
It doesn't get easier or cheaper than Now.