Fixed assets are those expenses on products that are going to have a useful life of more than one year in the economic activity. For example, if you buy a laptop, it is assumed (by the law) that you will be able to use it for your work for an average of 4 years.
Mind that to be a fixed asset they must:
Have a useful life of more than 1 year
Be 100% related to the economic activity
Be essential for its development
What does it mean that an asset must be "related" to economic activity?
When we say that an expense or a fixed asset must be "related" to the activity, we mean that it must be used solely and exclusively for the development of the activity. It is necessary to clarify the asset level of affection to correctly apply the tax regulations with respect to the deductions in function of each tax (personal income tax or VAT).