Embedding Google Sheets - 1

There are several ways to embed Google Sheets in a Google Site. This page and its sub-pages demonstrate at least some these.

Insert From Drive / Embed by URL

Sample spreadsheet to demonstrate embedding in Sites

This embedded spreadsheet 

This spreadsheet is embedded using the Insert 'From Drive' option. There are limited formatting options. ie You can select which tab to display and that's it.

Note that using the Embed 'by URL' option with the URL of the spreadsheet gives identical results.

Embedding link using HTML iframe

More flexibility is possible using HTML iframes. 

This embedded spreadsheet 

This is the same spreadsheet as above embedded using Embed 'Embed code' without parameters:
Goto the spreadsheet, click on the 'Share' button and Copy Link

Then add this link into the embed code box using an iframe tag in the form: 
<iframe height="hhh" width="www%" link </iframe>

The example shown here was done using:
<iframe height="400" width="100%" src="https://docs.google.com/spreadsheets/d/1sqLhj7oWGPEU7vjm-SfD55jqJEi0h47CPeDcILtDUVE/edit?usp=sharing"></iframe>

However, as can be seen, the result is a bit 'busy' as it shows the top menu and edit tools etc.

There is a subpage to this page showing some of what can be done to change what is displayed using various parameters

Embedding using 'Publish to the web' HTML

This embedded spreadsheet 

From the spreadsheet, select File > Publish to the Web, select what you want to publish and Web Page, click Publish and copy the Embed code which will look something like this:

<iframe src="https://docs.google.com/spreadsheets/d/e/2PACX-1vT2mDU-NxQHNlqzAM5UfVI3T9Bcza7DuTL9X61bqgpM9XZH0iRkcDtddRLTQADgIOzTgyUmkm__MV0i/pubhtml?gid=0&amp;single=true&amp;widget=true&amp;headers=false"></iframe>

Add height and width parameters as required e.g.

<iframe height="400" width="100%" src="https://docs.google.com/spreadsheets/d/e/2PACX-1vT2mDU-NxQHNlqzAM5UfVI3T9Bcza7DuTL9X61bqgpM9XZH0iRkcDtddRLTQADgIOzTgyUmkm__MV0i/pubhtml?gid=0&amp;single=true&amp;widget=true&amp;headers=false"></iframe>

to generate an embed like that shown here.

See also the URL parameters listed on this page