source: https://helpx.adobe.com/after-effects/using/blending-modes-layer-styles.html
Photoshop provides a variety of layer styles—such as shadows, glows, and bevels—that change the appearance of a layer. After Effects can preserve these layer styles when importing Photoshop layers. You can also apply layer styles in After Effects and animate their properties.
Note:
You can copy and paste any layer style within After Effects, including layer styles imported into After Effects in PSD files.
In addition to the layer styles that add visual elements—like a drop shadow or a color overlay—each layer’s Layer Styles property group contains a Blending Options property group. You can use the Blending Options settings for powerful and flexible control over blending operations.
Though layer styles are referred to as effects in Photoshop, they behave more like blending modes in After Effects. Layer styles follow transformations in the standard render order, whereas effects precede transformations. Another difference is that each layer style blends directly with the underlying layers in the composition, whereas an effect is rendered on the layer to which it’s applied, the result of which then interacts with the underlying layers as a whole.
When you import a Photoshop file that includes layers as a composition, you can retain editable layer styles or merge layer styles into footage. When you import only one layer that includes layer styles, you can choose to ignore the layer styles or merge layer styles into footage. At any time, you can convert merged layer styles into editable layer styles for each After Effects layer based on a Photoshop footage item.
After Effects can preserve all layer styles in imported Photoshop files, but you can only add and modify some layer styles and controls within After Effects.
Note:
For details about each layer style and its properties, see: https://helpx.adobe.com/photoshop/using/layer-effects-styles.html
Adds a shadow that falls behind the layer.
Adds a shadow that falls inside the contents of the layer, giving the layer a recessed appearance.