A Lagna is simply the Rasi that rises on the eastern horizon at the time of birth. This is an integral point of reference for a vedic astrologer. It denotes the self and personality. Houses are calculated from Lagna as a starting point. The Lagna lord is used to study ones traits or characteristics. Of course there’s more to Lagna than just reading personality traits, it has other interesting facets, eg; Arudha Lagna, Upapada Lagna , etc. As this is a basic study, I would not be venturing deep into Lagna.
Om Tat Sat