The squirmer model describes a spherical microorganism propelling itself by surface deformations. The key parameter β = B₂/B₁ distinguishes: pushers (β<0, bacteria-like, extend flow behind) and pullers (β>0, algae-like, extend flow in front). β=0 is a neutral squirmer. The far-field flow is a Stokeslet + force-dipole.