A full download (780K) includes the SciTE executable, any required DLLs, configuration files and documentation. After downloading the file, unzip it, and run SciTE.EXE. The files required to run SciTE are SciTE.EXE, SciLexer.DLL, and SciTEGlobal.properties and these are best located in one directory on the path.
A single file executable called Sc1 (480K) does not need any DLL or properties files as these are linked into the executable. You may still create properties files if you wish. Sc1.exe has been compressed with the UPX compressor so that it is a fast download. It does not need to be decompressed to be used.