Electricity can circulate in many things! In metals, electricity is a movement of electrons. However, an electric current can also circulate in a solution, the earth, the ocean or even our body: in these cases, electricity is transported by charged atoms or charged molecules (ions). So materials or solutions where electricity can circulate are conductive.

In metals, electricity is transported by electrons. An electron is itself charged (negatively), so a flow of electrons causes a transport of electricity.

In a solution, it's ions which carry electricity! The positive ions, with one or more electrons less, are therefore attracted by the origin of the electricity (the terminal - of the battery). However, negative ions, with one or more extra electrons, are rather repelled by this flow of electrons (and therefore attracted by the terminal + of the battery). This allows the circulation of electricity in a solution.