1 Introduction to KP theory and KP solitons.- 2 Lax-Sato formulation of the KP hierarchy.- 3 Two-dimensional solitons.- 4 Introduction to the real Grassmannian.- 5 The Deodhar decomposition for the Grassmannian and the positivity.- 6 Classification of KP solitons.- 7 KP Solitons on Gr(N,2N)≥0.- 8 Soliton graphs.- References.