A fluorescent filter is a color-correction filter. Fluorescent lighting often has a green cast, so these filters are usually magenta to counteract that and shift the light closer to daylight or tungsten balance (for example, FL-D or FL-W types).

That pink tint you saw is expected: the filter is adding magenta to compensate for green fluorescent light.

For film photography, these filters were useful because you couldn’t change white balance after loading the film. For digital cameras, they’re usually not necessary because you can correct color using white balance settings, a custom Kelvin setting, or by adjusting the RAW file later.

So: yes, the filter has a purpose, but for most digital shooters it’s rarely worth using. In many cases, setting white balance correctly—or overpowering bad fluorescent light with flash or using different lighting—is a better solution.