Anarcho-communism: Anarcho-communism is a society characterized by a high degree of cooperation, cooperation for mutual benefit, the absence of exploitation, the absence of economic classes, and the absence of a state that enforces class distinctions and class privilege. More importantly, anarcho-communism would feature the absence of coercion, direct or indirect, soft or hard, overt or disguised.
Anarcho-communism differs from anarcho-individualism in that anarcho-individualism would be a society characterized by a low degree of cooperation and a high degree of individual self-sufficiency, still with the absence of coercion. Anarcho-anything of course differs from conceptions of society that permanently or essentially privilege classes and exploitative relationships.
Anarcho-anything cannot be "implemented"; it will simply "occur" when most people have a naturally conforming political, social and individual psychology, and those who do not have a naturally conforming psychology recognize that conformity is more pragmatically valuable than subversion or resistance.
Anarcho-communism is, I think, best viewed as a "thousand-year" goal of contemporary communists. It's not necessary in this view to understand how anarcho-communism would work in precise detail; we can let our descendants work out the details to their satisfaction. It serves, rather, as a "flag in the sand": are we moving today (or in the near future) closer to (good) anarcho-communism or farther away (bad)? If we find a better goal later -- perhaps more or less modest -- we can always change it.
Anarcho-communism can emerge from "governmental communism". Governmental communism is, like anarcho-communism, characterized by cooperation for mutual benefit, and the absence of classes and a class state. Governmental communism retains coercion to enforce relations of mutual benefit. Governmental communism must combine literal democracy (rule of the people) with strong social and political constructions (e.g. constitutional provisions) that prevent majorities from exploiting minorities.
Governmental communism can emerge from "state communism". The goals of state communism are to eliminate class distinctions by absorbing the capitalist class into the working class, to promote literal democracy, ahd to establish the social and political constructions that allow a literal democracy to function without majoritarian exploitation. Marx's plan was to establish a class state compliant to the interests of the working class, since only the working class can absorb all other classes. To successfully transition to governmental communism, state communism must sail between the Scylla of privileging a governmental class in opposition to the working class and the Charybdis of the workers giving state power back to the capitalist class because of obsolete social and political constructions inherited (or adopted from) from capitalism. (The argument that the USSR and the PRC never were state communists is to argue that they intentionally and directly sailed straight for a privileged governmental class (USSR) or a thinly disguised capitalist bourgeoisie (PRC), a position I do not believe holds up in light of the historical evidence. They ended up there, but I don't believe it's plausible that they intended to end up there.)
State communism must emerge somehow from our present circumstances of capitalism. ("state" capitalism in an analogous sense to "state communism" above: a capitalist society that uses the power of the government to enforce and maintain class distinctions and the privilege of the capitalist class). The transformation of capitalism to state communism is, of course, a complicated and difficult endeavor.
This transition is aided by the fact that even as we speak, capitalism is collapsing at a fundamental level. For a lot of reasons (which I'll write about soon) the present crisis is very different from any previous capitalist crisis, however severe, including the Great Depression of the 1930s. However merely because capitalism itself is failing does not mean that the state communism will inevitably emerge; the transition to state communism requires the conscious intention of actual human beings to actively implement it. And it is not enough for communists to simply bring down capitalism (or let it fail); we must bring it down in such a way that a communist state — a communist state immune to, or at least less prone to, the dangers noted above — emerges from the collapse.