A “withhold” is a legal concept which the Florida Supreme Court has recognized as being a means to withhold the adjudication of guilt (conviction) even though you have been found guilty by a Court. It is recognized as a matter of Florida law but this is not necessarily true as far as other jurisdictions are concerned (i.e. other sovereigns, be them States or not, do not have to recognize the “withhold” as a legal entity and may, as the federal court system chooses to do, instead consider a withhold to be the very same thing as a conviction).
In Florida you do not have to admit to being convicted if you only have a withhold, but if you are asked about the withhold and you do not fess up then you are likely to be branded a liar.
Further, insofar as background checks go, many withholds can be sealed but you may still need to disclose even a sealed case, depending upon where you are applying, what you are applying for and the nature of the application question asked.
For example, your very case: The question asks “have you ever been convicted of a crime even if adjudication has been withheld” and, again, the only accurate answer is: “No I have not been convicted of a crime but yes I have received a withhold of adjudication.”, and you can expect this answer to raise additional questions.
My advise: A) Answer accurately and carefully and B) consider either attaching either or both a copy of the police report and / or a certified disposition of your case along with an explanation. While some employers will disqualify you for merely having been arrested (much less receiving a withhold) almost all will appreciate your honest disclosure. Moreover you will “take the wind out of the sails” by telling them about your past up front rather than them finding out about it afterward during a background check.