According to the Ornament of True Realization,
The arousing of bodhichitta is the wish, for others’ benefit,
To attain perfect Buddhahood.
It is the wish to attain perfect enlightenment in order to establish all sentient beings on the level of Buddhahood.
Its cause is threefold: (1) faith in the Buddha, (2) compassion for sentient beings, and (3) learning of the benefits of bodhichitta.
The contributory factor that helps bring about bodhichitta is having the courage and superior motivation to take upon oneself alone the great burden of the welfare of all beings, without exception.
In essence it is the wish to be capable of liberating all beings by attaining perfect enlightenment.
Bodhichitta can be classified in various ways, with four categories based on the different levels of the path, from the ordinary individual’s level of earnest aspiration up to Buddhahood, twenty-two categories indicated by similes, and so on.
However, the most widely known and easily understood are the two categories based on their characteristics. These are:
(1) Bodhichitta in aspiration, which is the wish to attain Buddhahood and is analogous to wanting to go somewhere; and
(2) Bodhichitta in action, which is diligence in the two aspects of bodhichitta, being the means for accomplishing Buddhahood, and is analogous to actually going.
The Way of the Bodhisattva describes them as follows:
Bodhichitta, the awakened mind,
Is known in brief to have two aspects:
First, aspiring, bodhichitta in intention;
Then, active bodhichitta, practical engagement.
As corresponding to the wish to go
And then to setting out,
The wise should understand respectively
The difference that divides these two.
“To arouse bodhichitta,” declares the Bodhisattva Levels, “is to focus on enlightenment and to focus on sentient beings.” In other words, bodhichitta focuses, on the one hand, on seeking the primal wisdom of the Great Vehicle, and, on the other, on the four boundless attitudes.
Arousing bodhichitta embodies aspiration and action, combining the mind turned toward enlightenment and the compassion that supports it.
Source: Rinpoche, Dudjom. A Torch Lighting the Way to Freedom (pp. 169-170). Shambhala. Kindle Edition.by