Please help need to understand deferred tax

I am studying for p 2 and feel like I am running out of time……pls help me understand deferred tax especially the tax bases of assets and liabilities. I was doing a question from BPP and got it wrong……also when they say tax deduction will be allowed or already allowed how does that affect your tax base…..any help will be appreciated…..also let me know if there are any study groups for p 2 that I can join ….thanks