A tire air pump is a tool to keep in your emergency roadside kit. They're also called inflators or air compressors, although there are small technical differences. They provide compressed or pressurized air to fill up tires to the proper Pressure per Square Inch, or PSI. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.