Renormalization Group Flow I am reading a book on effective field theory where the following "renormalization group equation" is given:

Now a quick search on google shows a bunch of interesting pictures of "renormalization group flows":

My question is: what is the relationship between the RG equation and the RG flow? In the picture, what is the "time parameter" of the flow, and what is being "flowed"?
 A: RG time is usually introduced as a dimensionless parameter like e.g. $$\Lambda\equiv\Lambda_0\mathrm{e}^{-t},$$
where in this convention $t=0$ corresponds to the ultra-violet (UV) at the initial momentum scale $\Lambda_0$ (which might be asymptotically large/infinite) and $t\rightarrow\infty$ corresponds to the infra-red (IR) with $\Lambda\rightarrow0$.
The RG equation in the question encodes Wilson's RG approach of integrating out momentum modes successively. Fluctuating fields are split into high (H) and low (L) according to their momentum. $S^\mathrm{eff}(\Lambda')$ is obtained from $S^\mathrm{eff}(\Lambda)$ at the higher scale $\Lambda$ by integrating out the high momentum modes $\phi_H$ with momenta $k\in(\Lambda',\Lambda]$. Higher momentum modes with $k>\Lambda$ are already integrated out in $S^\mathrm{eff}(\Lambda)$.
The RG flow is the change of (the couplings in) $S^\mathrm{eff}(\Lambda)$ with the RG scale $\Lambda$ or equivalently RG time $t$. For simplicity, practicality or sometimes physical reasons usually the flow of a few couplings (in many cases one coupling: e.g. the running coupling of QED or QCD in their perturbative regimes) is considered. RG flows are depicted or sketched in the typical diagrams one finds when googeling "RG flow". Usually not as functions of $t$ but rather as parametric plots in the space of couplings.
