Uppercase/ Captial Letters
are used to start a sentence or important words,

A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z

http://www.studyzone.org/testprep/ela4/i/impatica/namesoflettersofalphabetl.html

http://pbskids.org/lions/rock/abcow.html

http://www.studyzone.org/testprep/ela4/i/recognletternamesp2.cfm