Vanatru is a subset of Germanic Neopaganism concentrating on a family of Gods known as the Vanir.  They are often typed as "nature Gods", although this is oversimplifying things.  The Vanir are typically associated with fertility, as well as prosperity and peace.

The word "Vanatru" was coined in the mid-1990s, but was only used by a small handful of people; it began to gain popularity as a movement from 2007-2008 onward.  Up until that time Heathenry had mainly focused on the Aesir.  A growing number of people found themselves leaning toward the Vanir, and finding that the Vanir were different from the Aesir in terms of aesthetics, customs, and values.  It became necessary to differentiate between Vanatru and Asatru for the sake of clarity and accurate communication. 

The only real criteria for calling oneself Vanatru is to be "true to the Vanir" - whether one has a Vane as a patron, or is focused on these Gods as a pantheon.  That said, the word is patterned after the word "Asatru", and it remains the case that even if many Vanatruar are open to personal gnosis about the Vanir, exploring Vanic traditions in ritual, or seidhr, most Vanatru-identified people still identify with Heathenry, and most Vanatruar (including Wiccans and Druids who use the label of "Vanatru") are still practicing within a framework of cosmology, theology, praxis, and terminology resembling that of Asatru.

As the Vanatru movement has grown, we have seen a minority who do not fit the Heathen paradigm but used the word "Vanatru" for lack of a better religious label.  The term Waincraft has since been coined to accommodate some of them, as well as avoid further confusion about Vanatru, and a few of the personalities at the forefront of the Vanatru movement have taken to identifying with Waincraft as a direct result.  However, in polytheism, such diversity is to be expected, and the relationship between Vanatru and Waincraft is that of sister religions rather than conflict.  It is likely that Vanatru will continue to be the dominant form of Vanic Paganism.

It is, of course, entirely possible for someone to have a Vane as patron or focus primarily on the Vanir without applying the label of Vanatru to themselves, and some choose not to do so for various reasons.  Nonetheless, it has become a viable option for those looking for an outlet for Vanic religious expression.

Further reading:

• Seidhr
• Vanic Traditions for Today