"Miscible" is basically "mixable." In the context of the property of substances, miscibility is the ability to form a homogeneous solution. What homogeneous solution means in plain language is that the substance can mix in all proportions. Most usually the word "miscible" is used in relation to liquids but also applicable to solids and gases.
In contrast, "soluble" means the substance (solid, liquid or gas) can dissolve in another solid, liquid or gas. In plain language, dissolvemeans one substance becomes incorporatedinto another substance. Also in contrast to miscibility, solubility involves a saturation point, at which the substances involved can no longer dissolve any further and then a mass (the precipitate) begins to form.
For example, if you mix water and alcohol together, you can keep adding and mixing and the resulting liquid will continue to remain in liquid form. By contrast, if you dissolve sugar in water, the sugar will keep dissolving until it reaches saturation, and then additional sugar won't dissolve but remain a mass in that sugary solution.