what is the meaning of at least one head or tail and at most one head or tail in theoritical probability?

Answer :
We know :  Theoretical Probability of an event is the number of ways that the event can occur, divided by the total number of outcomes.  It is finding the probability of events that come from a sample space of known equally likely outcomes.

We can understand that by taking an example , As :

Example :  Two coin tossed , Probability of appearing at least one head or tail and at most one head or tail .

So, If two coin tossed sample space  = { ( T ,T ) , ( T ,H )  , ( H  , T ) , ( H , H ) }

Here meaning of at least one head or tail is , We can have minimum 1 head or tail .  So , That we get

We can get at least one head or tail  = 3 (  As ( T ,T ) , ( T ,H )  , ( H  , T ) for at least one tail And ( T ,H )  , ( H  , T ) , ( H , H ) for at least 1 head )
And
Probability of getting at least one head or tail = $\frac{3}{4}$

And

Here meaning of at most one head or tail is , We can have maximum 1 head or tail .  So , That we get

We can get at most one head or tail  = 3 (  As ( T ,T ) , ( T ,H )  , ( H  , T ) for at most one head And ( T ,H )  , ( H  , T ) , ( H , H ) for at most 1 tail )
And
Probability of getting at most one head or tail = $\frac{3}{4}$