  The physical interpretation of the main notions of the quantum group theory
(coproduct, representations and corepresentations, action and coaction) is
discussed using the simplest examples of $q$-deformed objects (quantum group
$F_q(GL(2))$, quantum algebra $sl_q(2)$, $q$-oscillator and $F_q$-covariant
algebra.) Appropriate reductions of the covariant algebra of second rank
$q$-tensors give rise to the algebras of the $q$-oscillator and the $q$-sphere.
A special covariant algebra related to the reflection equation corresponds to
the braid group in a space with nontrivial topology.
