Lambics, beers originating in the valley of the Zenne (in an around Brussels) Belgium, though copied by brewers in other parts of the world, may be refermented with cherries to make kriek, or fermented with raspberries to make framboise.
All kind of Lambic beers, topfermentation beers such as Belgian Golden Ales, Belgian Ambers and Flemish old brown beers usually go through a multiple stage fermentation process. After the first fermentation of the wort, sugar is added and the beer is refermented, on wooden casks. To make fruitbeer the fruit, fruit juice or fruit syrup is added (instead of sugar) to the first brew and refermented, these may be termed fruit lambics or fruit beers, depending on the type of first brew.
Beer that has fruit syrup or fruit lemonade added after (the finale stage of) fermentation, in other words as a flavouring are termed "Radlers" ("Shandy" in the UK) definitely not fruit beer.