What is "proto-writing"

Proto-writing refers to the early writing systems that emerged in Eurasia in the early 3rd millennium BCE that were a development based on earlier traditions of symbol systems that cannot be classified as writing proper, but have many characteristics strikingly similar to writing. They used ideographic and/or early mnemonic symbols to convey information yet were probably devoid of direct linguistic content. These systems emerged in the early Neolithic period, as early as the 7th millennium BCE.