Mini-Z's are 1/28 scale radio controlled cars, originally made by Kyosho. The scale has grown in recent years with a few other manufacturers such as PN, GL Racing, and Atomic making dedicated chassis. Realistic scale bodies are available from Kyosho, and aftermarket Lexan bodies are also available.
Most Mini-Z's are powered by 4 AAA rechargeable NiMH batteries and brushed motors. Higher end 1:28 cars are powered by lithium batteries and brushless motors. A wide array of chassis, suspension, and powertrain upgrades are available from manufacturers such as PN Racing, GL Racing, Atomic, and Reflex Racing,
A basic ready to run Mini-Z with radio transmitter included can be had for as little as $175.
Having the correct tires is by far the most important tuning tip for your car. Recommended tires for our track are:
Rears: Marka MZR-V1R10 for stock/super stock, MZRV1R05 for super stock/modified
Fronts: PN KS or KS-M Mediums (trued to 22.5-22.8mm to start)
This list of YouTube intro videos will be helpful in getting started