The "nature" of turbulence is discussed in relation with the strength of confinement effects. Examples from Rayleigh-Benard convection are given. For strongly confined systems, the framework of low-dimensional dynamical systems is fully adapted and the classical scenarios of transition to temporal chaos are obtained. In weakly confined systems, the degrees of freedom gain a functional nature, i.e., envelopes describing modulated patterns. The dynamics of textures can then be expressed using generalized phase variables and structural defects and the emerging spatio-temporal chaos can be interpreted in terms of phase and/or topological turbulence, at least as long as no subcritical instability is involved. A different scenario can develop when an inverse bifurcation takes place, with domains of different local regime coexisting ill physical space separated by fronts. The transition can then occur via spatio-temporal intermittency, a contamination process akin to directed percolation. The critical nature of the process and its universal content are discussed using coupled map lattices and their reduction in terms of cellular automata.
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