How do I edit this layers

The "stacked images" icon indicates this is an image sequence; it's a piece of footage. From what you've shown, there are also multiple copies of the same files on the timeline - probably using different blending modes, etc. for compositing. 

When you say "edit," what is it you're trying to achieve? Changing this piece of footage to a different piece of footage? Changing some of the properties of this layer? 

So I downloaded this template for my current project in After Effects, but it turns out that some of the layers in the timeline look like this, and I don't know how to edit it. Can anyone please help me with that?

By @Nana_Abakah

Hello, @Nana_Abakah 

Let’s unravel the mystery of those enigmatic layers in your After Effects timeline.

Layer Selection and Arrangement:
To select a layer, you can:
Click the layer directly in the Composition panel.
Click its name or duration bar in the Timeline panel.
Right-click (Windows) or Control-click (macOS) over the layer in the Composition panel if it’s obscured.
Type the layer number on the numeric keypad (if you know it).
To arrange layers, consider:
Changing the layer stacking order (which affects render order).
Use Ctrl + Down Arrow (Windows) or Command + Down Arrow (macOS) to move to the next layer.
Use Ctrl + Up Arrow (Windows) or Command + Up Arrow (macOS) to move to the previous layer.
Hold Shift while clicking or dragging to select additional layers or deselect them.
Editing Layers:
Cutting Keyframes:
If you want to keep keyframes at the same times, select the layer properties containing those keyframes.
Choose Edit > Cut.
Move or stretch the layer to its new In and Out points.
Move the current-time indicator to where the first keyframe appeared before cutting.
Choose Edit > Paste.
Changing Layer Properties:
In the Timeline panel, you can adjust a layer’s duration, starting time, and its place in the stacking order.
You can also modify any other properties of a layer directly in the Timeline panel.
Bonus Tip: Quick Layer Trimming:
Press Cmd + A to select all layers.
Move the current time indicator to the end of the composition.
Press Alt + ] to move the out point of your layer to the end.

Remember, even in the world of digital layers, you’re the director of your composition.

I hope this info is helpful to you.

Best Regard,
Ramon Reyes
myAARPMedicare