Welcome. There are actually many denominations that carry the name Lutheran. If you look at some of the sticky threads you will find key statements in detail.
Primary focal points:
Justified by grace through faith in Jesus Christ
(often said: grace alone, faith alone, and Scripture alone)
Proper Distinction between Law (what we are to do and not do, and the punishment/condemnation that results) and Gospel (what God does for us through Jesus Christ, in his perfect life, in his suffering and death on the cross to pay for the sins of the world, in his resurrection, ascension, and coming again to take all believers to heaven)
God works through means (instruments), namely His Word, Baptism (Matt 28:18-20; Acts 2:38-39, Acts 16:31-33; 1 Peter 3:21), and Lord's Supper (Matt 26:26-28; Mark 14:22-25; Luke 22:19-20; 1 Cor. 10:16; 1 Cor. 11:23-30).
Everything else flows from these.