It is most likely white fungus. Not any tyoe of fungus. For the most part it is relatively harmless and won't have any adverse effect of the inhabitants. It is just very annoying and In My Opinion it looks unsightly. It will be found in many tanks with live plants along with driftwood, that have been added to the tank recently.
You can just remove the objects that the fungus is on, and just wipe it off. Along with washing the onjectm and placing it back. But it is very common for it to reappear sometimes. There are two types that occur, posting a picture will help us Identify the type, and provide specifics on it.
Do you have any driftwood?
Were the plants recently added?
Can you provide any pictures?