  We provide a review of non-topological solitonic solutions arising in
theories with a complex scalar field and global or gauge $U(1)$-symmetry. It
covers Q-balls, homogeneous charged scalar condensates, and nonlinear localized
holes and bulges in a classically stable condensate. A historical overview is
followed by the discussion of properties of solutions, including their
stability, from different perspectives. Solitons in models with additional
massive degrees of freedom are also revisited, and their relation to one-field
Q-balls is showed. We also discuss theories with a gauge field giving rise to
gauged Q-balls and theories with dynamical gravity giving rise to boson stars.
