Scale represents a fraction of real size.
A vehicle that is 16 feet long in real life, will be 1 foot long in 1/16th scale.

Scale Most used for Example Best for
1/16 Farm toys.  Older and smaller farm tractors are 8 to 10 inches long, many newer models are more than 12 inches long, you are about 4.4 inches tall. Most are great for kids.  Collector and Precision models are intended for display rather than play.
1/18 Cars and small trucks. The 'typical' car is 10-12 inches long. Most are designed for display and have small, breakable pieces.
1/25 Trucks, cars, banks, and some construction equipment. Delivery trucks are 8 to 10 inches long, construction toys are a large 12 inches or more. Most items are built for older children or for adult collectors.
1/32 Farm toys and airplanes. Classic biplanes have about a 12 inch wingspan.  Farm tractors are smaller but still big enough for little hands. Old semi rigs are 14-16 inches long.  You are just over 2 inches tall. Most items are suitable for play.
1/34 Mostly First-Gear trucks Almost exclusively for adult collectors.
1/43 Farm toys, cars, and trucks. The same scale as a Lionel railroad.  Trucks and cars are 3.5 to 4.5 inches long. Great for older children, many items have small parts.  This scale is sought after by 'O' scale rail-road enthusiasts.
1/48 Airplanes Common scale for smaller airplanes. Some suitable for older kids.  Mostly collectibles.
1/50 Construction toys Dozers average 5 to 6 inches in length, graders and scrapers are 6 to 8 inches, cranes and large excavators are still 8 to 12 inches and up.  You are about 1.4 inches tall. Mostly for older children or adult collectors and modelers.
1/64 Farm equipment, semi trucks Farm tractors are between 3 and 4 inches long, a semi tractor with trailer is about 12 inches long. Great for all ages.  Small size makes this scale popular with kids and collectors.
1/72 Airplanes Popular scale for airplanes.  Still too large for modern most bombers and passenger jets. Some suitable for older kids.  Mostly collectibles.
1/87 Wide variety Same scale as HO railroads.  Large variety of trucks, equipment, and accessories available. Great for anyone old enough to have an HO train set.
1/144 Airplanes Common scale for larger planes. Some suitable for older kids.  Mostly collectibles.
1/400 Airplanes A 747 is only 6 inches long.  Used for only the largest aircraft. Strictly for collectors.