This is a masyu puzzle, one of the more popular Nikoli logic puzzles. In a masyu puzzle, the aim is to draw a single closed loop which goes through all circles in the puzzle. The loop must go straight through all squares with a white circle, turning 90 degrees in one or both of the adjacent squares. It must also make a 90-degree turn in every square containing a black circle while traveling straight through the two squares on either side. Since this is a fruit-themed puzzle, the black circles are apples and the orange circles are oranges.
The completed masyu puzzle is shown here:
The completed loop passes through most of the squares in the grid, but three of them are encircled instead. These containe the Japanese katakana
These katakana represent the sounds BA, NA, and NA, which gives the solution BANANA.