Concentration refers the amount of acid or base present in a given amount of solution. A concentrated solution is one that contains a large amount of acid or base in a given volume. A dilute solution is one that contains a small amount of acid or base in a given volume.
Strength
Acid strength refers to the degree the acid is ionized in a solution to form hydronium ions. A strong acid is one that is completely ionized in an aqueous solution. A weak acid is one that does not completely ionize in an aqueous solution.
Base strength refers to the degree the base is ionized in a solution to form hydroxide ions. A strong base is one that is completely ionized in an aqueous solution. A weak base is one that does not completely ionize in an aqueous solution.