Concentrated vs Dilute:
Amount of water added to the acid. High concentration means lots of acid particles and few water particles.
Strong vs Weak:
This depends on the chemical makeup of the acid.You cannot make the strong acids weak or the weak acids strong.
What is an acid:
An acid releases hydrogen ions into a solution (H+)
The stronger the acid the more ionised it is. Hydrochloric acid is completely ionised whereas ethanoic acid is only partially ionised.