Interplanting is a growing method that will allow you to fit more vegetable plants in a single planting bed. It is a way to increase your crop yield. Interplanting is also called intercropping.
Interplanting is often used in intensive vegetable gardening where an effort is made to use all available space in the growing area--the counter point to single row planting which requires the most cropping space since the space between rows goes unplanted. (In intensive gardening you can space plants individually equidistance apart or in wide rows--several plants across a row to as much as 4 feet wide.)
There are several ways to interplant your crops. You can grow fast-maturing plants, such as radishes, between slower growing ones, say chard. The radishes will be ready for harvest before the chard begins to mature and requires more space to spread out. This way of interplanting borders on succession cropping--bringing one crop to harvest after another keeping the planting bed productive all season.
You can also interplant crops with different growing habits, tall crops near short ones, or deep-rooted with shallow-rooted. Crops interplanted by growing habit can be set equidistant according to their size (height and breadth or root depth) at maturity; or they can be planted in their own alternate rows in a wide bed.
Interplanting requires planning. You need to know the days to maturity for each crop and its height and breadth at maturity or its root depth at maturity. Do some planning on paper once you have decided on the crops you will be growing this season.