In terms of Ibaadat,
Saheeh basically means that the person does not need to perform the action again, on the other hand, baatil means that the person needs to perform the action again.
Example: In terms of Saheeh, if a person is praying Dhuhr and he met all the conditions before salaah, requirments of Salaah, then his salaah does not need to be performed again. As for Baatil, if person who is praying dhuhr does not meet one of the conditions, then his salaah needs to be performed again
In terms of Transactions,
Saheeh means that he is allowed to utilise the place, thing etc, but if it is baatil then he is not allowed to use it or utilise it
Example: If a person bought a house or he purchased it in a way that is halaal etc, then saheeh for him to use it, as for Baatil, then if the house is haraam or he purchased it in a way that it is haraam etc, then it is baatil for him to use it.