Difference between excise availed & excise utilised??

Here by excise you obviously mean Cenvat Credit of Excise:

Excise Availed or taken means booking the credit of the excise duty paid on purcahse of inputs(raw mat etc)

Excise Utilised means the utilisation of that excise duty paid on inputs for paying output excise duty or service tax on removal of goods from factory or rendering of services respectively.

So you need to pay lesser amount in cash when you utilise the credit of excise.

Availment means to take eligible credit of duty or tax in the Books only (Only a Book Entry)

Unilisation means, to have utilised such credit against final liability of duty or tax