Life Cycle Assessment (LCA) can assist in:
⎯ identifying opportunities to improve the environmental performance of products at various points in their life cycle
⎯ informing decision-makers in industry, government or non-government organizations (e.g. for the purpose of strategic planning, priority setting, product or process design or redesign),
⎯ the selection of relevant indicators of environmental performance, including measurement techniques, and
⎯ marketing (e.g. implementing an eco-labelling scheme, making an environmental claim, or producing an environmental product declaration).

There are four phases in an LCA study:
a) the goal and scope definition phase: The scope, including the system boundary and level of detail, of an LCA depends on the subject and the intended use of the study. The depth and the breadth of LCA can differ considerably depending on the goal of a particular LCA.
b) the inventory analysis phase: The life cycle inventory analysis phase (LCI phase) is the second phase of LCA. It is an inventory of input/output data with regard to the system being studied. It involves collection of the data necessary to meet the goals of the defined study
c) the impact assessment phase: The life cycle impact assessment phase (LCIA) is the third phase of the LCA. The purpose of LCIA is to provide additional information to help assess a product system’s LCI results so as to better understand their environmental significance.
d) the interpretation phase: Life cycle interpretation is the final phase of the LCA procedure, in which the results of an LCI or an LCIA, or both, are summarized and discussed as a basis for conclusions, recommendations and decision-making in accordance with the goal and scope definition.

EN ISO 14040: 2006 available here