Your set of assets will contains all the aspects of your brand's visual identity.
Each toolkit is unique to the business that uses it. However, you can usually find:
LOGO: A logo in a variety of colours and sizes
TAGLINE DEVICE : A supporting brand asset used alongside the logo that is usually either emotive, descriptive or both
COLOUR PALETTE : A range of colours synonymous with your brand
TYPEFACE : A set of fonts for both the logo and supporting copy
TONE OF VOICE & DESCRIPTIONS : Guidelines on the language you should use to create the right personality for your brand
IMAGERY & ILLUSTRATIONS : A visual range that provides the right impression to those who encounter the brand
PATTERNS & DEVICES : Shapes and patterns taken from a dissection of the logo
TEMPLATES : Standardised formats for any regular forms of communication including newsletters, presentations, reports, etc.