Inner-springs are the coiled metal wire structures that form the core of a mattress. There are a variety of synonym options that convey the same concept, including coil mattresses, spring beds, and pocketed coil mattresses. Furthermore, other words that capture the essence of inner-springs are innerspring mattresses, coil spring mattresses, or simply spring mattresses. These terms can be used interchangeably to describe the same type of mattress structure. Some mattress manufacturers also offer hybrid options, which combine inner-springs with other layers of foam or latex for added support and cushioning. No matter which term is used, inner-springs are a popular choice for many sleepers due to their durability, support, and affordability.