The country shaped like a boot on maps of Europe is Italy.
The familiar boot shape belongs especially to the Italian Peninsula, which projects into the Mediterranean Sea. Its “heel” is the Salento Peninsula, its “toe” is Calabria, and the Gargano Peninsula forms a spur on the Adriatic side. The Apennine Mountains run down much of the peninsula like a backbone.
Italy also includes the large islands of Sicily and Sardinia, plus smaller islands, so the entire country is not literally boot-shaped. The nickname refers mainly to peninsular Italy. San Marino and Vatican City are independent enclaves located within the Italian Peninsula.
A nearby geographic fact often confused with this one is that Sicily sits just off the boot’s toe, across the Strait of Messina. Mount Etna, on Sicily, is Europe’s largest active volcano.