Iso-quant:

The dots in the above Figure denotes the various combinations of (L, K) that the producer can pick up from form to produce. Among these combinations, there can be those, which produce the same level of output. Herein comes the concept of an iso-quant. An iso-quant is a locus of combinations of (L, K) that produce the same level of output 'q' (see Figure).  

In the above Figure,  q amount of output can be produced by the input combinations - (L₁, K₁), (L₂, K₂), (L₃, K₃). Joining these, we get an iso-quant, which is also denoted by  q . Therefore, we see that the same level of output  q  can be produced using different techniques - either more K, less L (e.g., technique A), or more L and less K (e.g., technique C).