Cells are the basic building blocks of life. Plants and animals are each composed of trillions of cells. Despite their microscopic size, cells are specialised structures. Plant and animal cells differ from one another and cells within plants and animals differ from each other.
Identification
Animal cells are round with an irregular shape. Plant cells are usually rectangular with a fixed shape. Additionally, animal cells have cillia -- small, hairlike features that allow the cell to move. Cillia are very rare (but not impossible to find) in plant cells. Plant cells contain one large vacuole, or fluid-filled sac, located in the cytoplasm. Animal cells have similar structures, but they are much smaller and more numerous.
Significance
The differences between the cells help the plant or animal function on a larger scale. The differentiation between the two is due to the difference in the way each organism lives, reproduces and dies. For example, the difference in the size and type of vacuole accounts for the way plants reproduce and aids in that function. This is not true of animal cells, thus the vacuole plays a different role.
Considerations
Plant cells contain different features that animal cells don't have. Plant cells have chloroplasts for manufacturing chlorophyll. Plant cells contain plastids -- small structures that aid in photosynthesis. Additionally, plant cells have a cell wall and a cell membrane, while animal cells only have a cell membrane.