Depending on whether you are using a standard <apex:inputField> tag or not, you may need to follow these instructions to get the native help text to show up (if that is your intent):
Note that if custom help is defined for the field in Setup, the field must be a child of an <apex:pageBlock> or<apex:pageBlockSectionItem>, and the Salesforce page header must be displayed for the custom help to appear on your Visualforce page. To override the display of custom help, use the <apex:inputField> in the body of an<apex:pageBlockSectionItem>.
This link might be helpful:
https://help.salesforce.com/apex/HTViewSolution?id=000181401&language=en_US (https://help.salesforce.com/apex/HTViewSolution?id=000181401&language=en_US)
regards,
Sourav
https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_compref_inputField.htm