The variation tree is an SGF file containing all games in the
hit list ordered by the continuation
from the search position. So, for example, if you searched
the pattern below the encountered continuations (A and
B) will be merged and grouped into a tree:
The variations are ordered by the number of times the variation is played. So line A always contains the most hits, B second most. This gives you some information about the most natural way to play in the given position.
You can set the maximum depth of variations in the Tree depth menu on the search board. Setting it to 30 would limit variations to a maximum of 30 moves (in tree terminology called nodes). Please note that the size of the variation tree grows both with the tree depth and with the hit limit. If the first is set to 100 and the latter to 500 the variation tree could grow to a possible 50.000 nodes (in case none of the encountered lines of play would merge). This might be too much for your SGF browser to handle.