What are Abrams tanks and why is the US sending them to Ukraine?

Ukraine war news: U.S. will send Abrams tanks

Ukraine to receive first Abrams tanks in September – Politico - Ukrainian World Congress

The U.S. and Germany pledge tanks to Ukraine, signaling heavy fighting ahead : NPR

EXCLUSIVE: Ukraine's M1 Abrams tanks could come from US stockpiles, official says - Breaking Defense

Why is the U.S. sending Abrams tanks to Ukraine, and why is it significant? - MarketWatch

US moving towards giving Ukraine Abrams tanks: Reports

Ukrainian troops to begin training on US-made tanks in next few weeks – POLITICO

U.S. closer to approving 'significant number' of Abrams tanks to Ukraine - POLITICO

White House approves sending Abrams tanks to Ukraine

A problem of logistics: is the US sending Ukraine the wrong tank?