The Transfer of Property Act deals with two kinds of interest vested interest and contingent interest. Vested interest is to be distinguished from contingent interest. When an interest is vested, the transfer is complete but when the interest is contingent, the  transfer depends upon a condition precedent. When the condition is fulfilled the transfer takes effect and that the interest becomes vested.

Difference between vested interest and contingent interest 

                     Vested interest
Contingent interest.
Section 19 defines Vested interest
Where, on a transfer of property, an interest therein is created in favour of a person without specifying the time when it is to take effect, or in terms specifying that it is to take effect forthwith or on the happening of an event which must happen, such interest is vested, unless a contrary intention appears from the terms of the transfer.

Section 21 defines Contingent interest
Where, on a transfer of property, an interest therein is created in favour of a person to take effect only on the happening of a specified uncertain event, or if a specified uncertain event shall not happen, such person thereby acquires a contingent interest in the property. Such interest becomes a vested interest, in the former case, on the happening of the event, in the latter, when the happening of the event becomes impossible.

                                              Fulfillment of conditions
Vested interest does not depend upon fulfillment of any condition. It creates an immediate right though the enjoyment is postponed to a future date.

Contingent interest is solely depend upon the fulfillment of any condition. If the condition is not fulfilled the  interest fails
                                            Effects of transferee's death
Vested interest is not defeated by the death of transferee  before he obtains possession.

Contingent interest is defeated by the death of transferee before he obtains possession.

                                   Whether transferable  and heritable ?
It is both Transferable and heritable. If the transferee of the vested interest dies before actual possession or enjoyment it passes to his heirs.
It is  Transferable but whether it is heritable , depends upon nature of condition.
It passes not on heir on the death of the transferee  received to transfer.
                      Present right of enjoyment.
There is present, immediate right even when its enjoyment is postponed.
There is no present right of enjoyment, there is mere a promise for giving such a right.

See also......full note on 1) Vested interest

                                    2) Contingent interest


See Also..