That is a great chart that EMM referred you to - self explanatory really. But I will add that the V is usually said to have 2 "legs" and a "hinge". The hinge has a relationship with both of the legs - but the legs do not have a (sexual or romantic) relationship with each other. The legs are referred to as "metamours" in respect to their relationship to each other (your partner's partner) and may or may not be friends, or even know each other (however, the general poly advice seems to be that it is best if the metamours at least know one another). If the legs were to become romantically involved, the V would shift to a "triad" in which all are involved with one another.
In regard to hetero-V's, an MFM has a female hinge with 2 male legs, and FMF has a male hinge with 2 female legs. There was recently a lengthy thread on this subject. While many couples come into poly with the hope of finding another female to join them in a V or triad (the search for the so called "unicorn" - because they are so rare, yet so sought after) - the consensus seems to be that the MFM V's are generally the most enduring and stable over time.
Al