Speaking as a ex-long term anarchist, anarchism is much more heterogeneous in its ideologies or political orientations. You have anarcho-communists who are, especially from the outside looking in, very similar to communists to the point of seeming identical.

Then you have tendencies like individualists, post-leftists, and egoists that are wildly different and in a lot of ways their politics can be so different that it's hard to find a common thread linking them to other anarchist tendencies.

Speaking in broad terms from here on:

Anarchists tend to give much more emphasis to hierarchies and their concept of the state whereas communists tend to emphasize class and class conflict (i.e. where you get the workers vs the bourgeoisie framing of issues and the whole "workers of the world unite - you have nothing to lose but your chains!" sort of thing).

This might come off as uncharitable and it's a statement of personal opinion more than a statement of absolute fact but in my experience but, when pressed to define their position, anarchists tend to agree in the necessity of a transitional state between what we have right now and their ideal end-point (anarchism or communism, generally this is seen as interchangeable in a sort of platonic sense) however the real distinction is in their timeframes for the necessity of a transitional state; most anarchists do not believe that you can have the revolution overthrowing capitalism on Monday and achieve an anarchist society on Tuesday but they object to how long a transitional state exists under a communist party.

If I were to be more charitable here I would have said "transitional steps" but, even going by a commonly agreed-upon anarchist definition of the state, they will generally describe a transitional state.

Regardless, the overwhelming majority of Marxists see the revolution as being the first step, then the hard task of setting a course from what we have today (or what we have overthrown today) towards achieving communism begins as we transition to socialism and build up the necessary social and material preconditions (think things like how goods are produced and how the whole political economy functions) to advance towards the end goal of a stateless, classless, moneyless society (i.e. communism).

To illustrate the idea of preconditions and material conditions, we can use the example of slavery. Slavery has been abolished (I think?) everywhere in the world. Yet there are more slaves in the world today than there were at the height of institutionalised slavery.

Why is that? Well, a Marxist would start from a place of analysis that the conditions that give rise to slavery have not yet been eliminated and as such all the laws in the world aren't going to be sufficient to eliminate slavery alone.

To extend this idea a little more, the program for creating a stateless, classless, moneyless society is hard to fathom. Rightly so. As is eliminating the conditions that give rise to slavery. But we can understand the "etiology" of slavery and make educated guesses about what sorts of policies and, ultimately, what kinds of societies would mitigate these conditions. We can enact changes and measure their impacts and then, using this information of whether or not it was successful (or if it had a Cobra Effect), we can then take another step forward or we can take a step backwards with the knowledge that the next step we take will actually advance towards the desired outcome. And onwards it continues until we reach that end goal eventually through a process of doing a lot of research, careful consideration, measuring outcomes, and the correcting of errors.

Anarchists don't have the same emphasis on material conditions and so they tend to expect that anarchism should be achieved in relatively short timeframes. Communists, on the other hand, see the timeframes as being far longer and, venturing a guess here, you could ask most communists if they saw a revolution today whether they'd expect to see communism achieved within their lifetime and they'd tell you no.