Answer:
The texture of igneous rocks is governed by a complex interplay of various factors, but the three most important factors are cooling rate, viscosity, and crystal content.
The term "cooling rate" describes how quickly lava or magma cools and hardens. Larger crystals will have time to form if the cooling rate is slow, giving the resultant rock a coarse texture. On the other hand, if the pace of cooling is quick, fewer crystals or none at all will develop, giving the rock a fine texture.
The capacity of the magma or lava to flow is referred to as viscosity, and it is determined by its composition, temperature, and dissolved gas content. More viscous magma or lava has a tendency to entrap gas bubbles, creating a vesicular structure with numerous tiny holes. Gas can escape from a less viscous magma or lava, creating a dense texture.
The percentage of crystals in the magma or lava is referred to as crystal content. The resulting rock will have a phaneritic texture with discernible crystals if there are more crystals present. The resulting rock will have an aphanitic texture if there are few or no crystals.