A: Good question Jibran. And great picture by the way! :)
The term "b/d" stands for "brought down."
The term "c/f" stands for "carried forward."
You will normally see "b/d" as "Balance b/d" at the top of a T-account.
"Balance b/d" is sometimes shown as Balance b/f ("b/f" means brought forward). These two phrases mean the exact same thing.
"Balance b/d" or "Balance b/f" shows the amount brought down (or brought forward) from a previous period - i.e. the opening balance of an account.
"Balance b/d" or "Balance b/f" also shows the closing balance as a line at the bottom of the account.
"Balance c/f" is just used as a balancing line to calculate the closing balance figure. It is shown on the opposite side of the closing balance (opposite to the final line that shows "Balance b/d" or "Balance b/f").
Hope that helps clarify those terms and what they're used for!
Check out my lesson on balancing T-accounts, which will give you a step-by-step breakdown of balancing a T-account, including the use of Balance c/f and Balance b/f.