Two different questions
Perimeter answers "how far is it around the edge?" — it's a single length, measured in units like metres or feet. Area answers "how much surface is inside?" — it's measured in square units, like square metres. They're computed from the same dimensions but capture completely different things about a shape.
The same perimeter, three different areas
Three rectangles can all have a perimeter of 24 units while covering very different areas. A 10-by-2 rectangle has perimeter 2×(10+2) = 24 and area 10×2 = 20. An 8-by-4 rectangle also has perimeter 2×(8+4) = 24, but area 8×4 = 32 — more than half again as much, from the same perimeter. A 6-by-6 square (perimeter 4×6 = 24) reaches area 36, the largest of the three — among all rectangles sharing one perimeter, the one closest to a square always encloses the most area.
A circle beats them all
A circle with the same 24-unit perimeter (its circumference) has radius 24 ÷ (2π) ≈ 3.8197, giving an area of about 45.8366 — larger than the 6-by-6 square's 36, and far larger than the 10-by-2 rectangle's 20. For any fixed perimeter, a circle always encloses more area than any straight-sided shape with the same boundary length; this is a real geometric fact (the "isoperimetric inequality"), not a coincidence of these specific numbers.
Why this matters practically
This is why a fixed length of fencing encloses the most yard space when bent into a circle rather than a long thin rectangle, and why, among rectangular plots, a nearly-square shape makes better use of a given perimeter than a narrow one. Perimeter alone never determines area — the shape matters just as much as the boundary length.