Dividers and spacers are used in an email template to break up the content.
A divider is normally something that the recepient can see, i.e a coloured line, dotted line etc.
A spacer is normally something that the recepient can't see, which just creates a gap between two peices of content.
To use a divider, simply grab the divider icon from the content section and drag it in to the email template.
Once you click on the divider, you can open up the divider properties on the right of the screen. Here you can change things like the colour, line type, width and height.
To use a spacer, simply drag the spacer icon in to the email template.
When you click on the spacer you will open up the spacer properties menu on the right. The only thing you can change here is the height of the spacer.